Agents of DecaffeinationThe following agents are commonly used in decaffeinating coffee:
This solvent may be used in two ways to decaffeinate coffee.
In the direct contact method, the green (unroasted) beans are placed in a rotating drum and softened by steam for approximately 30 minutes; they are then repeatedly rinsed - for about 10 hours - with methylene chloride, which removes the caffeine from the beans.
The caffeine-laden solvent is drained away, and the beans are steamed a second time, for 8 to 12 hours, so the remaining solvent can evaporate. Finally, air or vacuum drying removes excess moisture from the decaffeinated beans. Virtually no solvent residue remains after roasting the beans.
In the indirect contact method, sometimes referred to as the "water process," the green beans soak for several hours in a water/coffee solution at almost boiling temperature. Gradually the solution draws out the caffeine, as well as other flavor elements and oils, from the beans.
The caffeine/water mixture is drained away and treated with methylene chloride, which absorbs the caffeine. The resulting mixture is then heated to evaporate the solvent and caffeine. Next, the mixture is reunited with the beans, allowing them to regain most of the coffee oils and flavor elements. The solvent never touches the beans.
Another agent widely used is Ethyl Acetate.